Plasma wall interaction in long-pulse helium discharge in LHD - Microscopic modification of the wall surface and its impact on particle balance and impurity generation

LHD Experiment Group

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23 Citations (Scopus)

Abstract

Abstract Ultra-long-pulse helium discharge with ion and electron cyclotron heating (ICH + ECH) in the Large Helical Device (LHD) was achieved in a 48 min plasma (ne ∼ 1.2 × 1019 m-3, Ti , e ∼ 2 keV) with an average heating power of 1.2 MW. The temperature of the first-wall surface during discharges remained at nearly room temperature. However, even in ultra-long-pulse helium discharge, the discharge conditions cannot be said to be in a steady-state, because of two major issues interrupting the steady-state condition. One is the "dynamic change of the wall pumping rate" and the other is the "termination of the discharge with the exfoliation of the mixed-material deposition layers." Microscopic modifications, such as helium radiation damage and the formation of the mixed-material deposition layers composed of C (∼98%) and Fe (∼2%), on the plasma facing components (PFMs) were clarified to possibly influence the major issues.

Original languageEnglish
Article number48793
Pages (from-to)91-98
Number of pages8
JournalJournal of Nuclear Materials
Volume463
DOIs
Publication statusPublished - 2015 Jul 22

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering

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